[RogerTheCat]

I have the sigma 150 which I bought as it has the HSM and I felt that being longer would be an advantage. It also has IMO better build quality over the Tamron but it all depneds how well you treat your lenese. In hindsight I do not feel that the extra 60mm over the Tamron is much of an advantage and have on occasion wished that I had bought the Tamron as I can see advatages with its smaller size. I have seen pictures taken with the Tamron (karlos78 has one) and it produces fantastic results. One of the Photography magazines has a good write up/comparrison on macro lenses, of course the nikon won